CA1165148A - Motion transmitting device - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A motion transmitting device of the quadrant drive type has a wheel, preferably toothed, a plurality of independently movable elements for successively engaging the wheel, a datum member and an eccentric effecting eccentric relative motion between the wheel and the datum member. Connector pins movable in ovoid or circular holes in the wheel and datum guide the movable elements into and out of engagement with the wheel. The movable elements are not linked, as in a chain, but means are provided to prevent them from any tilting or substantial rotation with respect to the datum member.

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Description

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MOTION TRANSMITTING DEVICE

This invention relates to motion transmitting devices of the kind known as quadrant drive devices.

Quadrant drive motion transmitting devices, which may be used for speed changing, torque conversion and the like, are described for example in U.S. Patent Specifications Nos. 4,023,440 and 4,194,415 (Canadian Patent Nos. 1040891 and 1105741~ and Canadian Application No. 374406. In conventional gearing arrangements, engagement is provided normally only by one tooth at a time. In the quadrant drive devices, meshing elements are employed which may remain in driving engagement with wheel means through a substantial fraction of a cycle; drive may be effective over nearly a quadrant of arc on the wheel means. Such devices essentially comprise eccentric means, wheel means and ;~
independently movable meshing elements the movement of which is controlle~ by movement limiting means 50 that the meshing elements move in and out of engagement with portions of the wheel means. Reference may be made to the above-mentioned specifications for full descriptions oEsuch devices. In U.S.
20 Specification No. 4,194,415, it is e~plained that the meshing elements may comprise - `~
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links ~ith two or more teeth, these being l~nks of a chain. The present invention is directed to an ~mproved form of quadrant dri~e motion transmitting dev~ce in whic~ the meshing elements are independently movahle and need not be linked ~n a chain But in which it i5 still possiBle to retain the high efficiency arisin~
from pure rolling motion between relati~ely moving load-transmitting elements~ As will be apparent from the following descript~on, the present invention has particular advantages using a wheel with close-pitched teet~ or a frictionally-driven wheel and hence enabling high torque or speed ratios to ~e obtained.
According to one aspect of this invention, a motion transmittin~ device including eccentric means, wheel means, non-linked and non-rotatable independently movable elements adapted to engage said w~eel means and movement limiting means including a datum member with first profiles, second profiles In said independently mova~le : elements and individual connector eleménts each enga~ing a first profile and a second profile to ~e held in - captive dependency t~ere~y wherein rotation of the eccentric means causes said mova~le elements sequentially to become engaged with a portion of the wheel means and subsequently to Become disengaged therefrom, said indepPndently mova~le eI~ments Being individually guided I~B~
~ 3 --by said movement-limiting means within predetermined limits of orbital motion relative to said datum member such that one or more of said independently movable elements is/are in engagement with and stationary relative to a respective portion or portions of the wheel means, said first and second profiles constraining the independently movable elements to move into engagement with the wheel means and to remain in engagement therewith over an arc of less than a semicircle and disengaging means constraining the independently movable elements to disengage from and to remain disengaged from the wheel means over the remaining arc.

In this construction, unlike the arrangements of the aforementioned U.S. Specifications Nos. 4,023,440 and 4,194,415, the independently movable elements are not linked in a chain.
These elements are made non-rotatable, that is to say, they are prevented from any substantial rotational movement or tilting with respect to the datum member about any axis through the element parallel to the a~is of the wheel means. This ensures that the elements, when out of engagement, cannot tilt and foul the wheel means, and, when engaged, are not titled by the torque reaction of the wheel means. As will be .....

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descri~ed la~er, there are a num~er of wa~s in ~hich this non-rotata~ility can be ach2eved~ Ver~ con~eniently, it is obtained b~ providing tw~ of sa~d indivIdual connector elements for each o~ said independently movable elements.
Said independently movable`elements may ~e - arranged around t~e outside of the wheel means in ~hat will ~e referred to as a male configuration or they may be inside the wheel means in what will ~e referred to as a female configuration.
If a male arrangement is consi~dered in which the independently mova~le elements-l~e around the wheel means and are moved inwardly ~nto engagement with the ~heel means, th.en the radially inward portions of said first profiles and the radially outward portions of said second profiles can be shaped to hold the meshing elements out of engagement ~th the wheel means ov~r the required arc; these portions of the profiles thus form . the aforementioned disengaging means. Other forms 2Q of disenga~ing means may be employed, for example, springs bet~een adjacent ones of said ~ndependently mova~le elements.
As in known quadrant dri~e de~ces, cons~der~ng the three in~egers, nameIy the`eccentr~c maans, the w~eel means 116~8 and the datum member, any one of these three integers may be used as the input to the motion transmitting device and any otner one may be used as the output. The third integer may be a second input or a second output but, in general, is fixed.
In a male configuration, it is convenient to use the eccentric as the input and the wheel means as the output with the datum member fixed, assuming a speed reduction is required. ~he input and output are interchanged if a speed step-up ratio is required. For a female configuration, it is convenient to use the eccentric as the input (or output) and the datum member as the output (or input), the wheel means being fixed.

In the constructions of, for example, U.S. No. 4,023,440 and No. 4,194,415, use has been made not only of the imp]osive octant but, also, to increase the effective arc used for power transmission, use has been made of the explosive octant, which is a region where the meshing elements te~nd to move outwardly from the wheel means. In the arrangement of the present invention, by using only the implosive portion of the power cycle, those parts of the first and second profiles, which would be necessarily utilised if the explosive portion of the cycle is used, are now redundant and can now be used :
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to ensure positive disenga~ement. In t~e arrangement of the-present invent~on, the datum plate and connector means can constitute the only l~n~age between the meshing elements. There is no need for the me$hing elements to be further linked, for example by being formed as links of a chain as in the arrangements of the specifications referred to a~o~e, where the further linking serves to heIp control the movement of the links.
The indepen~ently movable"elements conven~ently are meshing elements ~aving teeth adapted to mesh with teeth on said wheel means. ~lte,rnatively however the independentlv movable elements and wheel means ma~ be adapted for frictional'engagement when the elements are moved into contact w~th the wheel means.
Each of the independent~y movable elements has to en~a~e the wheel means for torque transmission but ,must be capable of being moved radially with respect , to the wheel so that the element can be moved into and out of engagement with the wheel. When in engagement, there is no reIative motion between the wheel means and the element. T~e elements and wheel , .

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means preferahly have complementary mating surfaces to gLve a large rigid contact ~hen in engagement.
The wheel means may ~e a toothed wheel with evenly spaced teeth. In a male configuration, these are outwardly directed teeth whereas, in a female configuration, t~ey are inwardly directed teeth. Each independently mova~le element meshes with these teeth when in engagement with such a toothed wheeI and is conveniently referred to lQ as a meshing element. Such a meshing element may extend around an arcuate portion of the wheel embracing several teeth on the wheeI. Pxeferably in such an arrangement each meshing element is shaped 50 as to engage with all the teeth in the arc over lS which the element extends but, as will be apparent from the following description, the device would be operative even if the meshing element only had one - tooth engaging the wIleel ~n that arc. Multi-tooth engagement is preferred to share the load.
The teeth on the meshing elements and wheel means -are not gear teeth and do not transmit an~ Ioad whilst in relative mot~on~ The meshing elements, when in load transmitting engagement, do not move relati~e`to the ` ` : ~ ~; `

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~heel means. .It is thus possible to use simple.
and readily manufactura~le shapes for these teeth.
The teeth on the mesh.~ng elements are conveniently of inverted dovetail shape, ~acing radially inwardly of the wheel means and with the narrower end of the dove-tail radially innermost and the wheel means has recesses complementary to the teeth on the meshing elements, these recesses ~eing evenly spaced around the periphery of the wheel. If the meshing eIement has a plurality of teeth, I0 these are positioned to face ~nwardly for a male configuration or outwardly for a female configuration in appropriate radial directions ~ith respect to the centre o~ the wheel so that when one of the meshln~ -elements is pressed against a circumference of the wheel, it forms a perfect fit around an arc of the~ wh.eel and ~ecomes in effect part of the wheel.
The inverted dovetails serve to provide a per~ect joint ~etween the meshing elements and the wheel means in a similar manner to wooden joints made ~y machine tools where the doveta~l is inverted (as distinct from ... hand-made dovetail joints ~ere the dovetail has its larger end outermost to cause the joint to lock~. The in~erted dovetails are used in the present case so that the me~hing elements and wheeI means may move in and out .' ':
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o~ en~a~ement during each cycle~
~ ince the inverted doYetail ~oint provides full area contact between the adjoining flanks of adjacent dovetails, unlike meshing gear teeth, it becomes possi~le to make the dovetail pitches ~ery fine yet xetaining considerable strength in the joint. This is in addition to the inherent advantage of a plurality of dovetails heing meshed at any one time. It is thus possible to have Yery high ratios handling high torques with small unit size. The meshing elements are under no load while engaging and disen~aging from the wheel means and, because of the very small radius of gyration of the eccentric, 1 mm in the example descri~ed above, very high efficiencies are possible. In addition there i5 is pure rolling motion between all the ~orque transmitting elements, specifically the ~onnector elements engaging their pro~iles. For these reasons it becomes possible to build units which can accept very high input speeds.
As explained a~ove, in v~e~ of the very small eccentricities that are possible ~ith this configuration, taking the output ~ack to an ax~s concentric with the input can ~e done w~th a ve~y simple coupling; any one of a number of proprietary couplings on the market may be used.
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- 0 ~ith the arrange~ent of the present invention, the meshing elements are maintained in engagement with the wheel means only in the radially implosive portions of the-driving and reverse driving cycle.
The driving portion is within approximately an octant and the reverse driv~ng portion, o~ generally similar arcuate extent, lies over an adjacent arc of approximately an octant. Thus the engagement between the meshing elements and the wheel means extends over a region o~ approx~mately a quadrant of a circle. During thè remaining part of the cycle, the meshing elements are positioned by said movement-limiting means to be out of engagement with the ~heel means.
In a ~uadrant drive apparatus having teeth on meshing elements engag~ng a toothed wheel, if the.
number of teeth on the whe~l differs from the number of teeth tor teeth spacesl on t~e mesh~ng.eléments~ then the device forms a speed changing or torque conversion s~ste~ as is described in the aforementioned ~pecifications.

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~ 1.1--However, by using a plurality of teeth on each meshing el~ment and shaping the first and second profiles so that each cycle of orbital movement of the meshing element changes the position of that element with respect to the wheel by one tooth pitch on the whee~ a very high ratio may be obtained. It is convenient, in describing the preser.t invention, to consider a specific example. If the wheel has 79 evenly spaced teeth and if there are 20 meshing elements each with 4 teeth evenly disposed along an arc on the radially inward edge of the meshing element, this arc being a portion of the circle whose radius is identical to that of the wheel, then it is possible to obtain a speed ratio of 79:1. The movement-limiting means may comprise a datum plate having 20 holes con-stituting first profiles, through whic~ pass rollers,constituting the aforementioned connector elements, which rollers also each pass through a hole in a meshing element this hole constituti~g the aforementioned second profile. In a typical example, the pitch of the teeth on the wheel means (and on the meshing elements) might be 4 mm, measured half-way up the sides of the inuerted dove-tails. Then the holes in the aatum member would be dis-posed around the circumference of a circle ~ith the pitch of the holes be~ng 16 mm, plus an amoun~ represented by the radially outward disposition of these holes from the arc on the meshing elements at which the 4 mm tooth pitch is measured. This arF corresponds to ~' 11~5~

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' the radius of the circle of the wheel meansO
i; I~ is desi~rable that the eccentric means effectiny eccentric motion between the datum plate and the wheel means has a pitch of one quarter of the pitch of the teeth and thus the eccentricity would be l mm. In motion transmitting devices of this nature, if one considers the three integers namely the eccentric means, the wheel means and the datum member, one of these elements may be driven to provide a rotational input and another provides a rotational output. A third would provide the reference with respect to which the first and second rotate and would normally be fixed. As previously mentioned, it is convenient in a male confi~uration to fix the datum member. To obtain a speed reduction the ~ input may then be to the eccentric and the output taken from the wheel means. It will be readily apparent from the figures given above that the 0 ,ery s ~aL~ eccent~1c~t~ make~ it readily poAs:bl-- : , ' ' ~ '' ~13-to obtain ~ coaxial input and output using a veX~ simple form of coupl~ng, e.g. a flexible sha~t.
This high ratio can be achieved ~ecause the or~ital movement o~ the meshing elements, fox each cycle, gives an advance of one tooth which is, in this example, only one quarter o~ the number of teeth on a meshing eIement. It will ~e immediately apparent that friction drive constructions, by ~ppropriate choice of the magnitude of the orbital movement with respect to the circumference of the wheel means, can readily provide very high speed ratios.
It is preferred in a male configuration that the side flanks of the meshing elem~nt are stralght and ~orm radii to the centre of the wheel means when drivingly engaged to have firm engagement with ~heir - neighbouring elements in the implosive portion of the power cycle,and the reverse power cycle, that is to ~a~ ~hen the meshing elements are in enyaye-~;
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ment with the wheel. ~he elements can then support oneanother as in the stones of a circular arch. The radially inward forces acting on the elements in this implosive portion of the power cycle are very similar to the forces imposed by gravity on the stones of an arch, These inward forces hold the meshing elements in engagement with the wheel means. By using elements abutting one another as described above, they are prevented from tilting over relative to the wheel means when torque is applied, as occurs due to the abutment of one meshing element against an adjacent one. The meshing elements which are not located in,the implosive portion of a power cycle or the reverse power cycle will not be engaged with the wheel means. They are moved outwardly to be further away from the centre of the wheel means. Thus, in the example given above, there is room to accommodate a total of 80 teeth on the meshing elements and 79 on the wheel means even although the circumference of the arc of the circle on the -pitch line of the teeth of the meshing elements is 2Q identical to the circumference of the circle on which are disposed the inverted dove-tails on the wheel means. When the meshing elements are out of engagement, they move radially outwardly and will separate from one another.
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., ~. 1~--The disengagement of. tk~ me.shing element is controlled b~ the aforementioned profl~les wh.ich. are engaged by the connector elements~ These connector elements, as ~ill be ex~laIned later, conveniently are roller pins. The profiles are conveniently holes which are $uitably ~haped. As is expla~ned in.~.S. 4,194,415, these profiles are theoretically ovoid holes. Ihe ovoid sha~e is re-quired only h~Jever over part of the circu~ference of each hole.
-- Since the`radially inward portion of each hole on the datum is not ~eing used ~sl`nce only the implosive portion of a power c~cle is fieing usedI it is convenient to form this non-used portion of the hole in the sha~e of a se~i-circle. The same may ~e done with the radially outward portion o~ the ovoid hole on the meshing element.
With the construction descri~ed. a~ove, it is possi~le to retain large roller pins and for example it ~ould be possi~le to use pins e~uivalent in size to those which would be used with a 16 m~ pitcfi.chain loop in the arrangement of U.S.4,194,415 ~ut ~it~ a high ratio device having only 4 mm pitch meshing elements on the wheel means and meshing means as descr;bed above. The cross-sectional area of a roller pin for a 16 mm pitch is very much greater than that for 4 roller pins for a 4 mm pitch chain loop~ The manufacturing problems are `~

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ve~ conslde~a~ly simpli~ed~ Since.the ~ase locus l~ne of the holes form~ng t~le- fl~rst and s~cond profiles is constructed ~ox an ecc~ntric~ty of 1 mm and for 4 mm pitch teeth, ànd also since the. arrangement descri~ed above is a dou~le ovo~d conflg~rat~on with profiles in the mes~ing elements and 1~ tfie datum mem~er~ so that the ~ase loci in each case arë hal~ed compared with a single ovoid configurat~on of U.S.4,023,440, and furthermore since tfie roller pl~ i`s the size required for a 16 mm chain loop, the ~ase loc~ content of the ovoid hole ~ecomes very small relat~e to the circular content of the hole caused ~y the comparatively large radius of the roller pIn~ This means that the hole is necessarily much closer to cl~rc:ular form~ In practical em~odiments it ~ecomes possifil~ to utili~se circular holes ~ecause the base loci content of the ovoid hole becomes negligible~ Th~s departure from the theoretical ideal shape can greatly reduce the cost of manufacture . without significant loss and effic~ency. The inherent elasticity of the device accommodates the small inaccuracies created ~ t~e departure from the theoretically ideal shape..
A further advantage of this configuration is that, although t~e pitching of t~e roller pins or other ~1~6Sl~

- ~ connector elements is large compared with the pitch of the teeth on t~e wheel and meshing elements, because of the small eccentricity the radius of gyration is small. Thus the difference in the circumference of the roller pin and the ~oles is small which results in very low rolling speeds of the roller pins in their holes.
As previously mentioned, a part of the profile may not ~e used and this leads to the possibility, as will be explained later, of employing, on either the movable elements or the datum mem~er, of "open-loop"
profiles, that is to sav part ovoid or part circular profiles, thereby making poss~ble further economy of manufacture.

In tha forego~ng, reference has been made to first and second profiles. Each profile may be larger than the conn.~tor element ~usually;a pin) which engages it, there~y giving a "dou~le-ovoid" form of operation analagous in some re~pects to the dou~le-ovoid construction of the aforementioned U~S.No.4,194,415. However a "single-ovoid'` arrangement analagous to U.S.No.4,023,440 may ~e emplo~ed, t~e connector elements rolling around ei~her the first profiles ~ut ~è~ng journalled in the mo~able elements or rollLn~ around the second profiles and ~eing journalled in the datum mem~er~

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~ hilst, as has alxeady ~een explain~d, by modifying that portion of the profiles l'n the datum member and in the meshing elements w~ich would normally be used for the explosive portion of the power cycle so that these portions of the pro~iles are sem~-circular, it is possi~le to ensure disengagement of the meshing elements . . .. _ .
during the cycle apart from the parts constituting the power cycle and reverse power cycle.
When the meshing or other independently movable elements are disengaged from the wheel means, they can no longer act like keystones because their flanks no longer abut one another. In this condition there is a possibility of the disengaged meshing elements tilting.
Second movement limiting ~eans are therefore praferahly pr~ided to prevent such tilting. In one convenient form, each element has a tongue extending into a groove in the next adjacent element so as to limit tilting as the elements mo~e apart. Other movement limiting means may be used. For example, light compression springs may be located between the flanks of the meshing elements to ensure that they do not tilt and that all remain radially outwardly disposed away from the axis of tne wheel means. Such springs also serve to ensure that the elements move apart in the disengaged portion of the cycle.
One of the most convenient ways of preventing . . .
tilting ho~e~e~ i~ to mak~ use of t~o connecto~ pins for each of said independently mo~able elements~ This I!

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~pecific configuration eliminates any necessity fo~
abutment to control th~ ~e~hing ele~ents in the en~aged portion of the cycle. .
- The invention includes ~Ithin its scope a quadrant drive motion transmitting device having eccentric means, wheel means ~ith portions shaped to engage with independently mova~le meshing elements and movement limiting means including a datum member, the eccentric means being arranged to cause the meshing elements sequentially to enter into and su~sequently move out of engagement with portions of said wheel means, ~aid meshing elements being individually guided by said movement limiking means through independent connector elements and ~7herein, o~ the three integers comprising the eccentric means, the wheel means, the datum mem~er, one is connected to a rotational input, another is connected to a rotational output and a third is fixed characterised in that the ~heel means comprises a wheel With (mn - 1) evenl~ spaced stations for engaging meshing elements and in that there are m meshing ele~ents, each having an ~n~ardly facing poxtlon adapted to engage ~ith the ~Iheel over an arcuate extent of n stations on the wheeI, where m is an integer equal to or greater than 8 ~and prefera~ly equal to ox gre~ter than 16), n is an integer equal to or greater than 2 (and preferably equal to or greater than 4~ and furthermore .~

``` 31~51~8 --~o--characterised in that the meshing elements have side flanks shaped such t~at these elements, when in engagement with t~e wheel, form a rigid arch. The stations are con~en~ently outwardly directed teeth as previously descri~ed.
The movement-limiting means preferably includes, for each meshing element, a connector pin adapted to roll around a closed profile on the datum member and a closed profile on the meshing element.
As previously explained, the profiles may be shaped so that each meshing element is held out of engagement from the wheel means over an arc greater than 180 by suita~ly shaping the radially inward portions of the profiles on the datum member and the radially outward portions of the profiles on the meshing elements.
Preferably each meshing element has n teeth or is shaped to engage with n teeth on the wheel. It is desira~le but not necessary for all stations on the wheel in the power octant and reverse power octant to be filled. However the device will operate even if some stations are not occupied.

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~ n the following description, reference will ~e made ~o the accompanying drawings in which:-Figure 1 is a front elevation showingdiagram~atically a datum plate, wheel means, some S of the meshing elements and the associated connector elements of a motion transmitting device forming one embodiment of the invention;
Figures 2, 3 and 4 are each a front elevation, similar to part of Figure 1 but showing respectively three modified constructions o meshing elements;
Figure 5 is a ~ront elevation illustrating two meshing elements of another construction;
Figure 6 is a side v~e~ part:ly in section, of part of the device of Figure 5;
Figure 7 is a front elevation, similar to part of Figure 1 but showing a modified construction;
: . Figure 8 is a cross-section, along the line 8-8 of Figure 9, of a two-stage de~ice accordtng to the ~nvention, in which t~e second stage is a planocentric device;

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651~8 ~ ',~ . ' Figure 9 is a cross-section along the line 9-9 of Figure 8;
~ igure 10 is a diagram illustrating a simple.
mechanical construction for the experimental S determination of an ovoid profile;
~ igure 11 sho~s typical traces drawn ~y the construction of Figure 10;
Figure 12 illustrates a graphical determination of an o~oid profile for accommodating a cylindrical pin of a predeterm~ned diameter;
Figure 13 illustrates a prof-~le such as might be used in an embodiment of the present invention;
Figures 14 and 15 illustrate. another em~od~ment of the invention;
Figure 16 is a front e~evation illustratin~
a ~odification of the construction of Figure 14i . ~ Figure 17 is a further front elevation illustrating : a modification of the construction of Figure l;
Figure 18 is a ~iew s~milar to ~-gure 15 but illustrating a mod~fication; and Fi~ure$ 19 and 20 illu~trate respective.ly further mod~fications of a datum plate and of connector - .

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Referring to Figur~ 1 there ~s shown diagrammatically ~ motion transmitting device having a datum member 1 with an input shaft 2 and eccentric 3. The centres of the input shaft and of the eccentric are indicated at 4 and 5 respectiveIy. The eccentricity is the distance ~ . A wheel 6 is free to rotate a~out the eccentric, that is to say on the centre 5. This wheel, in this particular embodiment has 79 teeth 7. The spaces between the teeth are of inverted dovetail form, that is to say they have straight sloping sides which diverge in a radially outward direction symmetrically a~out t:he radius through the centre of the space. ~he devi.ce has 20 keystone-shaped mèshing elements 8 of which only some are shown in the drawings. The shape of these meshing el~ments is such that their flanking surfaces abut one another when the meshing elements are in contact with the wheel means forming a circular arc a~out t~e centre of the wheel.
Each ~eshing element has four radially inwardly extending ' - . ~ .

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teeth 9, the sh~pe of t~ese teeth ~eing complementary to the gaps ~etween the teeth on the wheel means~
Thus, when the meshin~ elements 8 are in engagement - with the wheel, as in t~e upper part of F~gure 1, -5 they abut one another to ~orm a rl'gid arch and engage with the wheel so that the elements and wheel together constitute a rigid assemfily~
The datum plate 1 has 40 holes lO constituting the aforementioned first profiles, these holes being evenly spaced on a circle around the centre of rotation of the input shaft. Each mesh~ng element has two holes 11, each constituting one of the aforementioned second profiles.
For each hole in each meshing element there is a roller pin 12 ~hich passes through the hole ll in the mesh~ng lS element and the corresponding hol~3 10 in the datu~ plate.
These roller pins const~tute the aforementioned ~ - connector elemenls~ -Tha inverted dovetail-shaped spaces ~etween the teeth on the wheel 6 lie on a pitch circle 13 which is centred on the centre 5 of rot~t~on of the wheel. The holes lo in the datum plate have design centres on a p~tch circle - l~ w~ich is centred on the centre of rotation 4 of the - input shaft 2. The pins 12 are roller pins w~ich roll ~round the peripher~es of t~e profiles of the holes lO

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and 11 and serve to control the position of the mesh~ng elements. A~ is xe~dily.~een in the lowe.r part of Figure 1, the meshing elements are constrained over part of the arc to lie out of engagement with the w~eel.
In the particular position shown at the. botto~ of Figure 1, the pins 12, unde.r gravity, rest on the lower periphery of the holes 10 in the datum member 1 and ~he elements 8, under gravity, rest on the pins 12. In general however, the sh.aping of the holes 10 and 11 1~ positively hold the elements 8 in or ou~ of engagement with the wheel 6 as necessary. The design centres of the holes 11 in the meshing elements, when they are drivingly engaged with the wheel, as in the top half of Figure 1, lie on an arc 14 of a pitch circle whose centre is 5; The longitudinal axes of the roller pins 12, when drivingly engaged, lie on an arc I6 of a circle whose centre 134 is disposed at ~ point equidistant hetween the .. points 4 and 5. For clarity the difference in positions of these arcs has been exaggerated in Figure 1.
The meshing elements 8 in the upper part of Figure -- - 1 are in the implosive portion of the power cycle and the reverse power cycle. This portion comprises approximately an octant (on the upp~r left side of the igure for the directions of rotat~on shown by the arro~s A and B) ~orming the dri~ing cycle and another adjacent octant-~towards the upper right of the figure) , . .

constituting the re.ve.rse driYing cycle. The elements shown at 18 in the lo~er part of the figure are in the disengaged portion of t~e cycle, In the construction of E'iguxe 1, assum~ng the datum - 5 plate 1 is held fixed, rotatlon o the ~nput $haft 2 drive$ the eccentr~c 3 and hence causes the wheel 6 to gyrate. The teeth 7 on the wheel 6 engage with the teeth 9 on the me$hing elements 8. This constructicn with 79 teeth on the wheel 6 and 80 on the elements 8 forms a speed reducing motion transmitting de~ice giving a ratio of .79:1 if the output i5 taken from the wheel. The meshing elements 8 are constraînad, by the connector pins 12 engaging the f~rst profiles in the datum plate and the second profiles in the meshing elements~
to move cyclically into and out of engagement with the wheel so that over a su~stantial arc of the wheel, the elements ~ remain in engagement with the wheel. The multlple tooth engagement of several meshing elements enàbles high torques to ~e transm~tted ~y the device.

2~ As will be described in further detail later, the profiles are shaped so that the mesh.ing elements are positively moved out of engagement from the wheel over the disengaged port~on of the cycle, the lower half ln the condit~on ~hown in Figure 1. Because they are positively disengaged in this way, there is no need to link the elements 8 ~nto a cont~nuous -~
1QOP~ as in the arrangements of the aforementioned , ~514~

U.S. Specifications Nos. 4,023,440 and 4,194,415 (Canadian Patent Nos. 1040891 and 1105741) and Canadian Patent Application No. 374406, where endless chain constructions are employed. This considerably simplifies the construction and assembly of the device. The elements 8, being non-linkedr are independently movable. However, because of their possible independent movement, in order to prevent them tilting and fouling the wheel when in the disengagenlent part of the cycle, the meshing elements are made non-rotatable, that is to say means are provided for preventing any element 8 from substantial rotational movement about an axis through the element parallel to the axis of the wheel. In the particular construction shown in Figure 1, substantial rotation of elements 8 is prevented hy the use of two pins 12 engaging separate holes 11 in each meshing element.
These pins 12 in conjunction with th~ profiles in the datum plate thus serve not only to guide and hold the meshing elements in engagement with the wheel during part of the cycle and to disengage the meshing elements and hold them disengaged during another part of the cycle but also to prevent any substantial rotation of the meshing elements.

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The two pins 12 for each ele~ent 8 nee.d not necessarily be located on a common c~rcle ahout the centre of the ~heel in order to pxeVent the element 8 from tilting. In principle., the two pins may ~e.
S located at any two po~nts sp~ced apart on the element.
In the constructIon of ~gure l, the meshing elements 8 furthermore cannot tilt w~en ~n the engaged position because they abut one anoth-.er over their flank.ing faces. By abutting in thi~s way, the e.lements 8 form a rigid arch.~ith the ~h.ole group of elements over this arc acting as one un~t transmitting tor~ue between the datum membe.r and the wheel. Provided that the elements 8 cannot t~lt, as is ensured by the provision for example of two pins 12 for each element, it is not essential that, in abutting one another, the elements 8 should h.ave area contact.
Fox example, the e.lements might ~e shaped as shown at 18 in Figure 2, having contact at l9 when they are in engagement with the whee.l 60 More genexally h.owever, provi~ded the elements cannot tilt, it is not essential that they should abut. Figure 3 is a ~i~, similar to part of Figure l, showing non-abuttin~ elements 8a which are genexally ~ .

... .
similar in other re$pects to those of Figure 1, heing pre~ented from tilting by ~he provi$ion of two pins~
Another way of preventing tilting of the elements 8 is illustrated in Figure 4. In this embodiment, each S element 8 has only one hole 11 and pIn 12 and each element 8 has a tongue 22 on one side flan~ of t~e element extending into a corresponding groove 23 on the next adjacent element. The tongues and grooves have sufficient length that the tongues do not completely disengage from the grooves even in the fully relaxed port~ons of the quadrant drive cycle, that is to say corresponding to the lower part of Figure 1. The tongues and grooves serve to prevent any tilting of the meshing elements in the dis~ngaged part of the cycle.
Figures 5 and 6 illustrate the provision of compression springs 20 ~etween t~e elements 8, these ~eing located in holes 21 in the lateral flanks of thé elements and serving to keep these elements apart in the disengaged portion of the cycle. These springs 20 moreover assist in pre~enting any tilt~ng of the meshing elements. The springs 20 also cause disengagement of these elements from the wheel.

' ~30~

. ~
- i, Figuxe 6 is a side vie~ o~ the device taken along a section plane extending axcuately through the connector p1ns 12. ~s seen in Figure 5, the datum mem~er 1 lies on both sides of the wheel 6. The pins 12 extend into both paxts of the datum member and pass through the elements 8. The springs 20 are seen in Figure 4 extending between the locating holes 21 in adjacent elements 8.
In each of the devices thus far described, the individual elements 8 or 8a are multi-tooth elements extending, when in the engaged position, around an arc of the wheel 6 embracing several teeth. The movement-limiting means constituted by p~ns 12 and holes 10, 11 cause the elements to eE~ect or~ital movements giving lS a relative movement between the element and wheel o~ one tooth per cycle. This can;be achieved even ~f the ; elements 8 are not multi-tooth elements.
~ iguxe 7 ~llustrates-the extreme conditi~n where the elements 8b each have only one tooth 24. In this i~ure, the elements 8~ are ~hown spaced apart in the engaged part of the c~cle and each is prevented from tilting or rotation relat~ve to the datum plate 1 ~y two p~ns 25 which enga~e in ovo~d or c~rcular holes 26 ~n the element 8B and in ovoid or circular .
.

1 4 ~

holes 27 in the datum plate 1. In this embodiment, the holes in each element are spaced radially, instead of circumferentially as in Figure 1. This construction is particularly advantageous with motion transmitting devices with lower torque ratios than that of Figure 1, for example with twenty elements engaging nineteen teeth 28 on the wheel. It will be noted that such a device, unlike the quadrant drive devices of U.S. Patent Specifications Nos.
4,023,440 and 4,194,415 (Canadian Nos. 1040891 and 1105741) avoids any necessity for the elements to be linked in a chain. The gear profile can be made very simple and hence the wheel can, for example, be of sintered metal construction as also can be meshing elements. The standard of finish of the components can be considerably relaxed compared with the aforementioned prior quadrant drive constructions as there is no relative motion of the elements 8b with respect to the wheel during the power transmitting part of the cycle.

It is generally convenient to employ a balanced ~0 construction with the wheel means located between two datum members or with a datum member located between two wheel means.

;~ 5 ~

In the construction of F~gure l and its modifications described above, reference has ~een made to the input - $haft 2; the output can be from the wheel 60 More generally, in such construction~ ha~ing a shaft 2, a ~heel 6 and a datum plate 1, ~n~ one of the$e three components may be used a$ the input, any other one as the output and the third may be fixed. The speed and torque ratios will depend on the choice of the input and output.
Referring to Figure l, if the output is ta~en from a rotating and gyrating element such as the wheel 6, it will often be desirable to provide means for bringing the rotary output back to an axis co-linear with or concent~ic with the axis of the input shaft. Known forms of "back-to-centre" couplings may be used for this purpose. ~ith high ratio ~otion transmitting devices of the present invention, the eccentricity can be very small and it may often be possible to use a very simple "back-to-centre"
coùpling such as,a flexible shaft. However a preferred 2~ form of couplin~, having a high efficiency, will be described with reference to Figures 8 and 9.
In Figures 8 and 9 is shown a motion transmitting device in which the tor~ue converter is essentially similar to that illustrated in Figure l, as previously described in considerable detail, together ~ith a double ~lanocentric device wh~ch brings back to centre the eccentrically rotating output of the first stage.

.

~ ~ ~65 ~4~

-3.3-The ~ir~t stage includ~$ the. input s~ft 2 ~hich - i~ fox~ed ~ith an eccentric po~tion 3 about ~hich.
bearingly rotates a toothed wheel 60 Datum plates . 40 and 42 are fixedly supported on the frame 41 of 5 the device. The wheel 6 and the datum plates 40 and 42 are similar to those pr~viously described in connection with Figure 1,- and they ~nterengage through . . ..... the meshing elements 8 and p~ns 12 as also previously de$cribed.
The wheel 6 is furth~r fixedly attached to cylindrical member 47 to ~hich, ln turn, are fixedly attached t~o first planocentric discs 36, which are therefore also eccentrically rotatin~. Betw~en them lie~ a second planocentric disc 33 which is fixedly 5ecured to output shaft 30, which is coaxial ~ith input shaft 2. Thus, both input and output shafts (and second planocentric disc 3:3) are rotating about the common axis 0-0, while the ~heel 6 and the first planocentric discs 36 eccentrically rotate about their .20 axis 0'-0', ~heir eccentricity ~eing the distance 0-0'= .
The first planocentric discs 36 and the s~cond planocentric disc 33 ha~e all the same number of holes 37, ~hich have a circular profile. The holes 37 of first planocentric discs 36 and-of the second planocentric disc 33 are coupled to one another by _ means o~ roller pins 34 which. are thus captive within ~, . ~ ` ' Otheir respective sets of holes.
- The centres of all hol~ 37 ~n ~ir$t planocentric discs 36 are equidistantly arranged a~out axis 0'-0', while the centres of all holes 37 on second planocentric disc 33 are equidistantly arranged a~out axis 0-0, the distance ~etween these two axes being the eccentricity ~.
The diameter of these holes 37 is given by the formula:
Diameter of hole 37 - diameter of pin 34 ~ ~.
A counterweight 46 conveniently counterbalances the forces caused ~y the eccentrically rotating masses.
T~is counterweight would be pos~tioned at other locat~ons along the eccentric 3, the most obvious being between the frame and the wheel 6, however the location shown in Figure 8 is a ~etter choice ~ecause it is located between the qyrating masses, which makes possi~le almost perfect dynamic balancing.
It mu5t be pointed out that this double planocentric arrangement provides not simply a constant velocity, back-to-centre, coupling means, but a very superior one, in fact, vastly superior to a conventional planocentric arrangement (having a single plate with holes) in that sL~ce th!s no~el arrangement makes , ` ' ' ' . ~ . i ``

possible a pure rolling motion of the captive rollers 34 within the holes 37, it reduces friction to a (theoretical) value of zero.

Although in Figures 8 and 9 one form of construction for bringing the motion back to the same centre as the input has been described, other forms of coupling for this purpose will be readily apparent.

As is explained in the aforementioned U.S.
Specification No. 4,194,415, the holes 10 and 11 of Figure 1 in the datum plate 40, 42 and meshing elements 8 respectively have theoretically to be of ovoid form in order to get pure rolling motion of the roller pins 12 around these holes during the operation of the device and also to obtain multitooth engagement. The shape of the ovoids depends on the eccentricity but this shape has to be imposed on a larger shape required by the pin diameter. It will be shown later that, in certain embodiments of this invention, it is practical to depart from this theoretical shape and have ~ircular holes.

The actual shape of the ovoid hole may be determined experimentally using a draughting machine or theoretically.
Both methods of determination have been described in Canadian Patent Application No. 374406. For the present purposes, reference will be made to an experimental technique.

\ - ~

Figure I0 is a "draughting ~ac~in~'t on which the shapes of such "profiles" will ~e determined and th~ir parameters explored. In this machine disc 49! is the "reaction element" on which the desired profiles ~ill be traced. These profiles will have l'design centres" on pitch circle Cp ~having its centre at 0).
Cs is the pitch circle o~ t~e "action element"
(having its centre at 0'~. Pitch circle Cs is smaller than pitch circle Cp and the two circles are displaced from one another ~y the eccentricity .
; The centres 0 and 0' are "fixed to earth", i.e.
they are axes ~fixed and stationary) a~out which Cp (and disc 49) and Cs may freely rotate, separately and independently from one another. Assume Cp and Cs to ~e discs, or pulleys, freely rotata~le about 0 and 0' respectively. A ~elt i5 placed around Cp and another belt around Cs ~oth ~elts encircling a common idler disc I, the spindle of which is also "fixed to earth", and a stylus is attached at point ~ on the periphery of Cs (point A being at the greatest overlap ~etween Cp and Cs above axis X'-X~. Now, if Cs is rotated, the stylus o~ it will trace on disc 49 curves o which an example lS shown in Figure 11. Note that these cur~es include a num~er of ovoid shapes, ' :' ~ .' ` `
, `` 11~51~

- ~uch number depending solely on the ratio of the two xadii o~ Cp and C~ while th2 s~ze o~ the ovoid ~the ovoid area shown cross-hatched) depends on the eccentricity . The angle ~ (see Figure 11~
depends on the ratio of the t~o radii of circles C and C .
P s However, the eccentricity in the left of Figure llis ~ ~ P4, while that in the right of Figure 11 is < P4, where P is the pitch of the ovoid holes on the datum plate.
From the "draughting machine" of Figure 10:.
deduce:
1. The shape of the "profile" we are seeking is an ovoid locus.
2. The stylus (connecting meshing element, or pin, having a diameter equal to ~ero) on Cs ~ill engage such an ovoid on Cp during a selected (design choice) fraction of a full rotation (360).
3. If such a stylus on C~ is "withdrawn" during the remaining portion of the above-noted selected ~raction of a full rotation (i.e. during the angle equivalent to the b-b trace~, this withdra~al could in practice correspond to a disengagement cycle, durin~ which the ` . ' ' ~, :, ~ . -, ` , .

~16514~

$tylus, i.e. the meshin~ connecting element, could "~ump over" (i.e. advance ~y) one, or more, teeth, there~y~ obtaining considera~le speed reduction.
~hen the ovoid portion is used in the device of the invention, disengagement must occur ~efcre 90, i.e. above the X'-X axis, or may occur after 90, i.e. belo~ the X'-X axis. The corresponding conditions to the above occur in Figure 11 right and left, respectively.
Once the actual d~ameter of the pins 12 of Figure 1 is determined, a series of circles having radii equal to that of the pins 12 are traced as shown in Figure 12 with centres right on the ovoid 55 thus arriving at the ovoid profile 56 around the outside of these circles. This is the actual "~orking profile" ~hen the pins have a given diameter.
If we form ovoid holes or profiles on the reaction element (datum plate~ and o'void profiles on the action element (meshing elements) and if we wish to have ~ pure rolling motion of the pins 12, we must 20~ exactly halve the size of the ovoid profile shown in Figure 1~ and we must also orient the two profiles (on the datum plate and the meshing elements~ in opposite directions, more preciseIy, their basal ends must point outwardly, i.e. away from one another.

.

. .
, ~ ' . ~.. .

`` ll~Sl~

As previously mentioned, a pure rolling motion of the pins 12, mean$ a (theoretical~ elimination of friction, a factor that greatly improves the overall efficiency of the mechanism.
S With the arrangement o~ the present invention uslng multitooth sagments, t~.e eccentricity may be made,much less t~an P and hence the ~ase locus of the -ovoid is small, as shown at the right-hand side of Figure.:ll. For these reasons, as the eccentricity gets smaller ~or a given pit.ch, the base locus ovoidal content of the ovoid hole becomes smaller in relation to the circular content created by the roller pin which has to ~e superimposed upon the base locus, but has not been correspondingly reduced in diameter since, in the example g~en,one pin works ' for four tooth pitches~ ;
' In the specific example given above with 4 mm pitch .- - of the teeth on the wheel and with 4 teeth on each meshing element, the pin diameter is quite large, being suitable for a 16 mm pitch chain loop but ~the eccentricity is only 1 mm. -In a double ovoid configuration, that is to say a configuration having holes in meshing elements and the datum plate each.of suitable pro~ile, the base loci for the ovoid holes ~5 is halved compared ~ith. a single ovoid arrangement.
, ' , , .

~1~51~

~40-Because of these factors the base loci content of the ovoid hole in the construction of the present invention becomes very small relative to the circular content of the hole caused by the comparati~ely large radius of the roller pin. The exact shape of the hole, from design considerations, is an ovoid departing only very, very slightly from a true circular hole. The difference is a small fraction of a m~llimetre. This is illustrated in Figure 13 where chain line curve 50 shows, in the upper half of the figure, an ovoid profile determined as described a~ove from a base locus 51 representing the radially implosive portion of the power cycle which is to ~e used. Curve 54 represents the xadially explosive portion which is not used and is substituted by semicircular profile 55. The working profile 50 is completed around the bottom part ~y a semicircular arc 52 since the shape of this part of the profile is not ~eing used in the power cycle, ~ut or disengagement purposes as previously descri~ed.
For comparison a semicircle 53 is shown as a full lîne around the upper part of t~e fi~ure. This shows how - ~mall is the deviation from a circle and thus why a circular hole can ~e used~ It ~ecomes possi~le, in a practical case such as ~as ~een descri~ed a~ove, to make use of circular holes, there~y ~acilitating the , .~, - .

.

- 1~65~

~manufacture~ without significant loss in efficiency.
The elasticity of t~e device accommodates small inaccuracies created hy the departure from. the theoretical shape. ~s previously explained, in ~iew of the small eccentricity, the or~ital locus of the roller pins, which, in the case of the previous example becomes circular, is small despite their relatively large size and hence this results in a very lo~ rolling speed for the pins and holes~ A further advantage arising from the small difference in the circumference of the roller pins compared with that of the holes in the datum plates and the holes in the meshing elements is that this greatlv reduces the Hertzian stress load ~that is to say stress loads due to repetitive reversal of load pressure on the surface~ on the surfaces of the walls of the holes and on l:he surfaces of the roller pins. This in tur~ reduces the chances of brinelling on these surfaces. ,-In the em~odiments thus far descri~ed, toothed meshing elements have been employed. Alternativelyfrictionally engaging meshing elements may be employed permitting of very high speed rat~os. Figures 14 and 15 are diagrams explaining such a device using a V~pulley and V-shaped frictional elements. Figure 14 is a sectional elevation and Pigure 15 is a transverse ~, . ' ' ~

.`653L~

-~2- .

section of a V-pulley 60 freeIy rotata~le on a needle-bearing (shown only in Figure 15 for clarityl on an eccentric 61 carried on an input shaft 62. A
plurality of wedge~shaped segments 63 are arranged - 5 around the pulley. Each segment has an ovoid or circular hole 64 through wh~ch passes a pin 65 of cylindrical section, the pin ~eing in rolling engagement with the profile of the ovoid or circular hole 64 and also with the profiles of ovoid or circular holes 66 in a pair of datum plates 67, one on each side of the pulley.
These datum plates are rigidly secured together to form the capturing plate assem~ly of a dou~le ovoid quadrant drive in which the segments 63 move cyclically into and out of engagement with the pulley 60.
The segments in Figures 1~ cmd lS each have a single hole 64 and pin 65 and each has a tongue 68 engaging a groove 69 to prevent relative tilting, as has been described with reference to Figure ~. Furthermore the segments a~ut one another when they are in engagement ~ith the pulley. Other arrangements may be employed `~ to prevent tilting, for example ~y using two pins per segment as in the con~truction of Figure 1~
Because a friction dr~ve~s employed, there is now no requirement to have`a cyclic displacement of one ". ~ ' - . .

~ 1~i514~
~43-tooth pitch and it becomes possibIe to obtain vary ~igh reduction ratio~. It ~ill be noted that, in the present arrangement, a large area of contact can be obtained between the flanks of the segments 63 and the conical surfaces 70 of th~ pulley. These axially facing flank surfaces of the segments (for example surface 71 in Figure 1~) are therefore made concave to conform to conical shape o~ the pulley~
It ~ill be noted that in this construction the roller pins 65 provide positive outward pull for positive disengagement of the segments in the appropriate part of the cycle. The choice of the numb~r of segments, the si~e o the roller pins and the radius of the pulley can be made as a function of the torque to be transmittecl and may be independent of the ratio required. With ~ery high ratios, tha eccentricity ~ecomes small and the ba~k-to-centre -` coupling can be of simple construction. Because of the small eccentricity, circular profiles can usefully be employed in this application ~or the reasons already ~iven, Provision may ~e made for a small adjustment of eccentricity to obtain t~e correct amount of friction.

.

` 1 1651~

In all the constructions described, a "double ovoid" arrangement has ~een employed havin~ ovoids ~n the meshing elements or $egments and in the datum means.
Because of the small eccentr~city which is used with - 5 high ratio devices of the present inVentiQn~ it may, ln many cases, be pre~erred to use s~ngle ovoid or circular profile arrangements. In other words the pins such as pins 12 of Figure 1 or the pins 65 of Figures 1~ and 15, might be journalled in either the datum means or the meshing elements and xol] around the periphery of an ovoid or circular ~ole ~n the other of these elements.
In the arrangements descr~ed, the meshing elements comprise a plurality of segments. It is not essential that all the segments in any one embodiment should be identical~ For example any one of the meshing elements 8 of Figure 1 might be replaced by two or more adjacent eleme~ts, each with its pin and ovoid or circular hole ox holesO .-Friction elements such as have been described with reference to Figures 14 and 15 need not necessarilyabut one another although a~utting elements, forming a xigid arch around the sector ~here they engage the wheel are generally prefexred. Figure 16 ~llustxates ~65 mod~fication of the con~t~uction of F~ure 14 but . emplo~in~ non~abuttIn~ e.lements 80 ~hich frict~onall~
engage the ~heel 6~ . In F~ure 16, each element h.as two apertures 81 recei~ng separate p~ns 82 to pre.vent the element$ 8~ from tilting. Other means, such as those preYiously descr~bed, may be emplQyed to pxeVent tilting o~ the elements 80 with respect to the datum plate 67~
The use o~ elements wh.ich are spaced apart in the part of the cycle. where they engage the wheel can be used not only ~s in Fi~ures 3 and 16, which are male configurations w~th the wheel inside the elements, but also in female configurations ~here the member with which.the elements engaye lies around lS those elements. In motion transmitting devices such.
as have been described, ~ is necessary to have an input, an output and a datum. T~e datum i$-usually f~xed although there are circumstances in which it can he a second input or a second output. In t~e male constructions described above, more particular reference has heen made to arrangements in which the input drives the eccentric, an output i~ taken frQm the wheel and .

.

5 14~

o there is a datum member which constrains the p~ns engaging the mova~le element~ Th~s datum member is therefore sometimes referred to as a capturing plate.
For consistency in language, the capturing plate or corresponding element ~ill still be referred to as the datum member. In the female configurations to be di~scribed ~ith reference to Figures 17 and 18, this capturing plate or datum member is used as the output. The mova~le elements corresponding to the elements 8 of F~gure 1 are moved into and out of engagement wit~ a surrounding female member which is referred to as the stator and which corresponds ~lth the wheel means of Figure 1 in that it engage.s the elements but would usually be fixed.
In Figure 17, an input sha;~t 2 drives an eccentric 3 rotatably carrying a cap~uring plate 90 in which there are a plurality of ovoid or circular apertures - 10 in Which are pins 12. These pins engage circular or ovoid holes 11 ~n movable elements 92. There are t~o pin3 per element to pre~ent any substantial rotational movement or tilt~n~ o~ these elements.
The elements.92 have out~rdly d~rected teeth.93, .

, ~ .

~ ~5 14~

.

convenien~ly of invexted doyetail form, ~h~ch me.sh ~ith corre$ponding inwardly directed teeth 94 on a fixed plate or stator 95. In this particular embodiment there axe twenty eIements 92 each.~ith ~oux 5 teeth 93 and there ar~ 81 teeth 53 on the stator.
The elements 92, when l'n mesh with the stator 95, are sufficiently far apart that they can be withdrawn inwardly to a disengaged positl'on. Orbital movement of the elements 93 is effected, by rotation of the eccentric 3 relative to the capturing plate 90, causing the latter to gyrate and so effecting the required orbital movement of the elements 93~ The ovoid or circular holes have profiles as previously de.~cribed to give positive engagement and di~sengagement in the appropriate parts of the cycle. The arrangement thus constitutes a "one-tooth d.ifferential" driving the capturing plate 90 ~it~ a speed reduction rat~o of - 1:80. In Figure 17, two pins 12 are used for each element 92 to prevent tilting ~ut one p;n per element may be used if tilting Is prevented by other means.
A ~riction drive a~rangement may also be constxucted ~ith a female conf~guration as shown in Pigure 18. Thi$ may conyen~ently be compaxed ~i.th Figure 15 showing a corre~ponding male construction~
In Figure 18, an ~nput shaft 62 dri~es an eccentric 61 on which is rotata~ly mounted a capturin~ plate as~embly 100 incorporating t~o paxallel plates 101 lying one on each ~de of the movable elements 1020 Pins 103 ext~nd each thxough an ovo~d or circular hole 104 in each of the. plates 101 and through an ovoid or circular hole 105 In the elements 102.
Conveniently there are two pins per element but it is possible to use only one pin per element if tllting is prevented by other means~ The elements 102 have side surfaces shaped to engage conical surfaces 106 in the stator. The elements must, when engaged, be spaced circumferentially to permit of them moving radially inwardly when so ~guided in their individual orbital paths by the p~ns 103 and hole.s 104,105.
As in the male frictional drive arrangement, the magnitude of the orbital movement of the elements 102 determines the amount of movement relative to the member (in this case the $tatorl with which these elements engage. This or~ital movement will ~e small ' `
, ,~ ~

~lB~
~ 49 -compared with the arcuate spacing of the elements and hence high speed ratios are readily possible.

It is believed unnecessary to describe further the operation of the female configurations; this is generally analogous to the operation of male arrangements previously described. Female constructions may have back-to-centre couplings as in male arrangements.

In all the embodiments thus far described, a "double ovoid" technique (see U.S. Patent No. 4,194,415 or Canadian No. 1105741) has been employed, that is to say there are ovoid holes in the meshing elements and ovoid holes in the capturing plate, the pins rolling around the peripheries of both holes. Particularly because of the small eccentricity which may be employed in embodiments of the present invention, it may be more convenient in some cases to use a "single ovoid" configuration (see U.S. Patent No. 4,023,440 or Canadian No. 1040891) in which the pins are journalled in the meshing elements and roll around respective ovoid holes in the capturing plate or are journalled in the capturing plate and roll around ovoid holes in the meshing elements.

The ovoid holes hold the pins in captive dependency.
A~ has been explained, each hole has a profile with tWo portions, one portion being shaped for moving the elements into engagement and holding them there and the second portion moving the elements out of engagement and holding them out of engagement, that is to say preventing them from moving into engagement in this part of the cycle. The second portions of the profiles, provided they ensure proper movement out of 1~ engagement, are not critical and, as previously explained are conveniently circular arcs. It is possiblq to use "open-loop" profiles (as distinct from "closed-loop" profiles~ so long as alternative disengaging means (suc~ as springs~ is provided in place of said second portions wh~ch have been removed to form the open loop. To ensure captive dependency, in general the open loops would be only on the capturing plates or only on the meshing elements but in certain circumstances - it may ~e convenient for the profiles to be open on both.

As previously explained, wit~ the small eccentricity possi~le using the present invention, the profiles may be circular arcs. Figure 19 illustrates an arrangement similar to Figure 1 but with open-loop profiles 110 on meshing elements 111 but closed-loop profiles 112 on a capturing plate (i.e. datum member) 113. Connector pins 114 engage with and are retained by the profiles 110, 112~ Figure 20 illu~txates an .

- ~ ~ 6 5 ~5 1~

. ~ . . .
arrangement similar to Figure 1 but with open-loop profiles 120 on a datum plate 121 and closed-loop profiles 122 on mes~ing eIements 123. Connector elements 124 engage with and are retained by the profiles 120, 122. Such open-loop profiles may facilitate manufacture and assembly of the device.
The pins and profiles in the constructions o~
Figures 19 and 20 operate, as described with reference to Figure 1, to control the orbital movement of the connector elements with respect to the wheel 6 and also, since there are two pins for each element, to prevent tilting of the elements. In both these configurations springs 125 provide the disengaging means.
All the arrangements employing teeth which have been described with reference to the dra~ings are "sin~le-teeth differential" constructions in which th`e male and female assembl;es effectively have n and n + 1 teeth respectively, although, as for example in Figure 7, teeth can be omitted from certain elements.
The single-tooth differential gives the largest speed ratio; obviously however if lower speed ratios are required it is possible to have a difference of more than one tooth on the male and female assemblies.

Claims (38)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A motion transmitting device including eccentric means, wheel means, non-linked and non-rotatable independently movable elements adapted to engage said wheel means and movement-limiting means including a datum member with first profiles, second profiles in said independently movable elements and individual connector elements each engaging a first profile and a second profile to be held in captive dependency thereby wherein rotation of the eccentric means causes said movable elements sequentially to become engaged with a portion of the wheel means and subsequently to become disengaged therefrom, said independently movable elements being individually guided by said movement-limiting means within predetermined limits of orbital motion relative to said datum member such that one or more of said independently movable elements is/are in engagement with and stationary relative to a respective portion or portions of the wheel means, said first and second profiles constraining the independently movable elements to move into engagement with the wheel means and to remain in engagement therewith over an arc of less than a semicircle and disengaging means constraining the independently movable elements to disengage from and to remain disengaged from the wheel means over the remaining arc.

2. A motion transmitting device as claimed in claim 1 wherein said wheel means is a male wheel and wherein said independently movable elements are arranged around the wheel means.

3. A motion transmitting device as claimed in claim 2 wherein said independently movable elements, when they are drivingly engaged with the male wheel, each abuts against its neighbours on flanking surfaces to form a rigid structure.

4. A motion transmitting device as claimed in claim 3 wherein said flanking surfaces of said independently movable elements are such that the elements are wedge-shaped forming a circular arch when in engagement with the male wheel.

5. A motion transmitting device as claimed in claim 1 wherein said wheel means is a female wheel and wherein said independently movable elements are arranged inside the wheel means,

6. A motion transmitting device as claimed in any of claims 1, 2 or 5 wherein said independently movable elements are spaced apart from one another when in driving engagement with the wheel means.

7. A motion transmitting device as claimed in any of claims 2, 3 or 4 wherein said disengaging means comprise springs between adjacent ones of said independently movable elements urging said elements apart.

8. A motion transmitting device as claimed in any of claims 1,2 or 5 wherein disengaging means are constituted by said connector elements and portions of said first and second profiles.

9. A motion transmitting device as claimed in claim 5 wherein the radially outward portions of said first profiles and the radially inward portions of said second profiles are so shaped as positively to hold the independently movable elements out of engagement with the wheel means over an arc of more than a semicircle.

10. A motion transmitting device as claimed in any of claims 2,3 or 4 wherein the radially inward portions of said first profiles and the radially outward portions of said second profiles are so shaped as positively to hold the independently movable elements out of engagement with the wheel means over an arc exceed-ing a semicircle.

11. A motion transmitting device as claimed in claim 1 wherein the independently movable elements are meshing elements each having a tooth or teeth adapted to mesh with a tooth or teeth on said wheel means.

12. A motion transmitting device as claimed in claim 11 wherein the wheel means is a toothed wheel with evenly spaced teeth.

13. A motion transmitting device as claimed in claim 12 wherein each meshing element, when in engagement with the toothed wheel, extends around an arcuate portion of the wheel embracing a plurality of teeth on the wheel.

14. A motion transmitting device as claimed in claim 12 wherein each meshing element, when in engagement with the toothed wheel, extends around an arcuate portion of wheel embracing at least four teeth on the wheel.

15. A motion transmitting device as claimed in any of claims 12, 13 or 14 wherein said first and second profiles are so shaped that each cycle of orbital movement of the meshing element changes the position of that meshing element with respect to the wheel by one tooth pitch on the wheel.

16. A motion transmitting device as claimed in any of claims 12,13 or 14 wherein each independently movable element is shaped so as to engage with all the teeth in the arc over which the element extends.

17. A motion transmitting device as claimed in any of claims 12,13 or 14 wherein the pitch circle of the teeth on said wheel has the same radius as the pitch circle of the teeth on said meshing elements in engagement with the wheel.

18. A motion transmitting device as claimed in claim 4 or claim 12 or claim 13 wherein the independently movable elements and wheel means have complementary mating surfaces to give rigid contact when in engagement.

19. A motion transmitting device as claimed in any of claims 12, 13 or 14 wherein the wheel means comprises a toothed wheel with evenly spaced teeth and with the gaps between the teeth of inverted dovetail shape and wherein the independently movable elements have teeth complementary to said recesses.

20. A motion transmitting device as claimed in any of claims 12 or 13 or 14 wherein said movable meshing elements each have a plurality of teeth, said teeth in said meshing elements being in the form of inverted dovetails which mate with complementary inverted dovetail shaped teeth in the wheel means.

21. A motion transmitting device as claimed in any of claims 1,2 or 5 wherein the independently movable elements and wheel means are adapted for frictional engagement when the elements are in contact with the wheel means.

22. A motion transmitting device as claimed in any of claims 1, 2 or 7 wherein the wheel means is a V-pulley and wherein the independently movable elements are shaped for frictional engagement with said pulley.

23. A motion transmitting device as claimed in any of claims 1, 2 or 2 wherein the wheel means is a V-pulley and wherein said independently movable elements have concave faces frictionally engaging conical flange surfaces of the pulley to be in area contact therewith.

24. A motion transmitting device as claimed in claim 5 wherein the wheel means has an inwardly directed V-groove into which said independently movable elements are moved to engage the wheel means.

25. A motion transmitting device as claimed in any of claims 1, 2 or 5 wherein said first and second profiles are so shaped that each cycle of orbital movement of one of said independently movable elements changes the position of that element with respect to the wheel means by an angular arc around the wheel less than the arc engaged by each element.

26. A motion transmitting device as claimed in any of claims 1, 2 or 5 wherein each connector element is shaped to roll along its associated first profile and its associated second profile.

27. A motion transmitting device as claimed in any of claims 1, 2 or 5 wherein each connector element is a cylindrical element of uniform diameter arranged to roll along its associated first profile and its associated second profile.

28. A motion transmitting device as claimed in any of claims 1, 2 or 5 wherein each of said first profiles has a design centre and all such design centres lie on the circumference of a circle.

29. A motion transmitting device as claimed in any of claims 1, 2 or 5 wherein each of said second profiles has a design centre and wherein the design centres of the second profiles of all elements in engagement with the wheel means lie on a circle or circles having a common centre.

30. A motion transmitting apparatus as claimed in any of claims 1, 2 or 5 wherein each of the first profiles is circular.

31. A motion transmitting device as claimed in any of claims 1, 2 or 5 wherein each of the second profiles is circular.

32. A motion transmitting device as claimed in any of claims 1, 2 or 5 wherein each of said first profiles is of ovoid form.

33. A motion transmitting device as claimed in any of claims 1, 2 or 5 wherein each of said first profiles is of circular form and wherein said connecting elements are cylindrical pins of smaller diameter than said first profiles.

34. A motion transmitting device as claimed in any of claims 1, 2 or 5 wherein each of said second profiles is of ovoid form.

35. A motion transmitting device as claimed in any of claims 1, 2 or 5 wherein each of said second profiles is of circular form and wherein said connecting elements are cylindrical pins of smaller diameter than said second profiles.

36- A motion transmitting device as claimed in any of claims 1,2 or 5 wherein the connector elements are guided by said first profiles and are journalled by said second profiles for rotational movement in said independently movable elements.

37. A motion transmitting device as claimed in any of claims 1,2 or 5 wherein the connector elements are guided by said second profiles and are journalled by said first profiles for rotational movement in said datum member.

38. A motion transmitting device including eccentric means, meshing means in the form of a series of non-linked and non-rotatable wedge-shaped elements each formed with a plurality of first teeth at the narrower end of said wedge-shaped elements, gear means formed with second teeth complementary to said first teeth, a datum member formed with first profiles of predetermined shape, said wedge-shaped elements being formed with second profiles of predetermined shape individual connector elements separate from one another, each engaged in loose captive dependency within said first and said second profiles, and wherein said eccentric means is disposed to cause said wedge-shaped elements to sequentially perform a wobbling motion in and out of meshing engagement with successive said teeth of said gear means while each said wedge-shaped element is guided within specific limits of said wobbling motion by said connector elements engaging within said first and second profiles, said meshing elements when drivingly engaged in the radially implosive portion of the driving and reverse driving cycle being so formed on their radial flanks to abut each against its neighbours to form a rigid circular arch and thereby to form a rigid structure with said wheel means and said meshing elements are drivingly engaged by the connector elements to remain out of engagement during the disengaged portion of the cycle.

39. A motion transmitting device including eccentric means, meshing means in the form of a series of non-linked and non-rotatable wedge-shaped elements with at least one tooth at the narrower end of each element, a datum member formed with first profiles of predetermined shape, each of said first-profiles having a first design centre with all such first design centres disposed on a first circle about a first axis, gear means formed with second teeth complementary to said at least one tooth, said second teeth defining a second pitch circle about a second axis, said wedge-shaped elements being formed with second profiles of predetermined shape, each of said second profiles having a second design centre, individual connector elements, totally separate from one another, each engaged in loose captive dependency within said first and second profiles, each of said connector elements having a longitudinal axis, wherein said eccentric means is disposed to cause each of said wedge-shaped elements, at its toothed end, to become engaged with, and subsequently to become dissociated from, said teeth, whilst said wedge-shaped elements are individually guided by said connector elements engaging said first and second profiles within specific limits of movement relative to said datum member, such that always one or more of said wedge-shaped elements are in engagement with, and stationary relative to a tooth or teeth on said gear means, and such that the total movement relative to said datum member of each of said wedge-shaped elements, whilst it is drivingly engaged with one of said second teeth, follows an orbital locus, which is the same as that of said gear means, said second design centres on those wedge-shaped elements which are stationary relative to the gear means all lying on the arc of a third circle which is concentric with said second pitch circle, said first and third circles intersecting one another, said longitudinal axes of said connector elements which are engaging wedge-shaped elements stationary relative to the gear means all lying on the arc of a fourth circle, having a third axis, any two of said first, third and fourth circles intersecting one another.

40. A motion transmitting device as claimed in claim 39 wherein all three said first, third and fourth circles intersect one another at the same two points.

41. A motion transmitting device as claimed in either claim 39 or claim 40 wherein said wedge-shaped elements are formed so that those elements, when in engagement with the gear means, abut one another to form a rigid structure.

42. A motion transmitting device as claimed in any of claims 38, 39 or 40 wherein each of said first profiles is circular.

43. A motion transmitting device as claimed in any of claims 38,39 or 40 wherein each of said second profiles is circular.

44. A motion transmitting device as claimed in any of claims 38,39 or 40 wherein each of the first profiles is ovoidal.

45. A motion transmitting device as claimed in any of claims 38, 39 or 40 wherein each of said second profiles is ovoidal.

46. A motion transmitting device including eccentric means, meshing means in the form of a series of wedge-shaped elements with first inverted dovetail-like teeth at the narrower end of each element, gear means formed with second teeth complementary to said first teeth, tilt limiting means arranged to prevent relative tilting of said wedge-shaped elements, a datum member, a series of individual movement-limiting means comprising first profiles on said datum member, and second profiles on said wedge-shaped elements with individual connector elements each engaging a first profile and a second profile to be held in captive dependency thereby, said movement-limiting means being separate from said teeth, said eccentric means being disposed to cause each of said wedge-shaped elements to become engaged with and subsequently to become dissociated from said gear means whilst said wedge-shaped elements are individually guided by said movement-limiting means within specific limits of movement relative to said datum member, such that always first teeth of a plurality of adjacent ones of said wedge-shaped elements are simultaneously engaged with, and stationary relative to, a corresponding number of said second teeth on said gear means, and so that the total movement relative to said datum member of each of said first teeth, whilst it is drivingly engaged with said second teeth, follows an orbital locus, said wedge-shaped elements being formed to abut against adjacent elements when in engagement with the gear means to form a rigid structure.

47. A motion transmitting device as claimed in any of claims 38 or 39 or 46 and having a male gear means wherein said first profiles have radially inward portions and wherein said second profiles have radially outward portions which are designed to provide positive disengagement of said wedge-shaped meshing elements.

48. A motion transmitting device as claimed in any of claims 1, 5 or 9 and having a female gear means wherein said second profiles have radially inward portions and said first profiles have radially outward portions providing positive disengagement of said elements.

49. A motion transmitting device as claimed in any of claims 2 or 38 or 39 wherein springs are provided between the independently movable or wedge-shaped elements for disengaging those elements from the wheel or gear means.

50. A motion transmitting device as claimed in any of claims 2 or 38 or 39 wherein springs are provided between the independently movable or wedge-shaped elements, said springs being arranged to prevent said elements from tilting relative to one another when disengaged from the wheel means.

51. A motion transmitting device as claimed in claim 1 wherein the independently movable elements are meshing elements each having at least one tooth adapted to mesh with a tooth or teeth on said wheel means and wherein the wheel means comprises a wheel with (mn - 1) evenly spaced stations for engaging said movable elements and wherein there are m movable elements, each having an inwardly facing portion adapted to engage with the wheel over an arcuate extent of n stations on the wheel, where m is an integer equal to or greater than 8, n is an integer equal to or greater than 2 and furthermore wherein said movable elements have side flanks shaped such that these elements, when in engagement with the wheel, form a rigid arch.

52. A motion transmitting device as claimed in any of claims 38 or 39 or 46 wherein the wheel means comprises a wheel with (mn - 1) evenly spaced stations for engaging said movable elements and wherein there are m movable elements, each having an inwardly facing portion adapted to engage with the wheel over an arcuate extent of n stations on the wheel, where m is an integer equal to or greater than 8, n is an integer equal to or greater than 2 and furthermore wherein said movable elements have side flanks shaped such that these elements, when in engagement with the wheel, form a rigid arch.

53. A motion transmitting device as claimed in claim 51 where m is an integer equal to or greater than 16.

54. A motion transmitting device as claimed in either claim 51 or claim 53 where n is an integer equal to or greater than 4.

55. A motion transmitting device as claimed in any of claims 38 or 39 or 46 wherein the wheel means comprises a wheel with (mn - 1) evenly spaced stations for engaging said movable elements and wherein there are m movable elements, each having an inwardly facing portion adapted to engage with the wheel over an arcuate extent of n stations on the wheel, where m is an integer equal to or greater than 16, n is an integer equal to or greater than 4 and furthermore wherein said movable elements have side flanks shaped such that these elements, when in engagement with the wheel, form a rigid arch.

56. A motion transmitting device as claimed in either claim 51 or 53 wherein the movement-limiting means include, for each said movable element, a connector pin adapted to roll around a closed profile on the datum member and a closed profile on the movable element.

57. A motion transmitting device as claimed in either claim 51 or claim 53 wherein the movement-limiting means include, for each said movable element, a connector pin adapted to roll around a closed profile on the datum member and a closed profile on the movable element and wherein each connector pin is cylindrical and wherein each closed profile is a circular hole of larger diameter than the connector pin.

58. A motion transmitting device as claimed in either claim 51 or claim 53 wherein said stations are formed by evenly spaced outwardly directed teeth on the wheel.

59. A motion transmitting device as claimed in either claim 51 or claim 53 wherein said stations are formed by evenly spaced outwardly directed teeth on the wheel and wherein each said movable element has n teeth or is shaped to engage with n teeth on the wheel.

60. A motion transmitting device as claimed in either claim 51 or claim 53 wherein the movement-limiting means are shaped so that each said movable element is held radially outwardly from the wheel to be out of engagement from the wheel over an arc greater than 180°.

61. A motion transmitting device as claimed in either claim 51 or claim 53 wherein said stations are formed by evenly spaced outwardly directed teeth on the wheel and wherein said movable elements and wheel have teeth profiles of inverted dovetail form.

62. A motion transmitting device as claimed in either claim 51 or claim 53 wherein said stations are formed by evenly spaced outwardly directed teeth on the wheel and wherein said movable elements are wedge-shaped with the flanking surfaces straight and, when the elements engage the wheel, radial with respect to the centre of the wheel.

63. A motion transmitting device as claimed in either claim 51 or claim 53 and having compression springs between said movable elements arranged to hold the elements apart in the circumferential direction when they are displaced radially outwardly from engagement with the wheel.

64. A motion transmitting device as claimed in any of claims 38 or 39 or 46 wherein the wheel means comprises a wheel with (mn - 1) evenly spaced stations for engaging said movable elements and wherein there are m movable elements, each having an inwardly facing portion adapted to engage with the wheel over an arcuate extent of n stations on the wheel, where m is an integer equal to or greater than 8, n is an integer equal to or greater than 2 and furthermore wherein said movable elements have side flanks shaped such that these elements, when in engagement with the wheel, form a rigid arch and wherein compression springs are arranged between said movable elements to hold the elements apart in the circumferential direction when they are displaced outwardly from engagement with the wheel.

65. A motion transmitting device as claimed in any of claims 1, 38 or 39 wherein said second profiles on the independently movable elements are of open loop form and wherein disengaging means are provided in addition to the movement-limiting means comprising the first and second profiles and connector elements.

66. A motion transmitting device as claimed in any of claims 1, 38 or 39 wherein said first profiles on the datum member are of open loop form and wherein disengaging means are provided in addition to the movement-limiting means comprising the first and second profiles and connector elements.

67. A motion transmitting device as claimed in any of claims 1, 38 or 39 wherein said first profiles and said second profiles are of open loop form and wherein disengaging means are provided in addition to the movement-limiting means comprising the first and second profiles and connector elements.

68. A motion transmitting device as claimed in any of claims 46, 51 or 53 wherein said second profiles on the independently movable elements are of open loop form and wherein disengaging means are provided in addition to the movement-limiting means comprising the first and second profiles and connector elements.

69. A motion transmitting device as claimed in any of claims 46, 51 or 53 wherein said first profiles on the datum member are of open loop form and wherein disengaging means are provided in addition to the movement-limiting means comprising the first and second profiles and connector elements.

70. A motion transmitting device as claimed in any of claims 46, 51 or 53 wherein said first profiles and said second profiles are of open loop form and wherein disengaging means are provided in addition to the movement limiting means comprising the first and second profiles and connector elements.

71. A motion transmitting device as claimed in any of claims 1, 38 or 39 wherein said movable elements are formed with co-operating tilt limiting means.

72. A motion transmitting device as claimed in any of claims 46, 51 or 53 wherein said movable elements are formed with co-operating tilt limiting means.

73. A motion transmitting device as claimed in any of claims 1, 38 or 39 wherein each independently movable element has a tongue extending into a groove in an adjacent element to limit relative tilting of the elements when they move apart.

74. A motion transmitting device as claimed in any of claims 46, 51 or 53 wherein each independently movable element has a tongue extending into a groove in an adjacent element to limit relative tilting of the elements when they move apart.

75. A motion transmitting device as claimed in any of claims 1, 38 or 39 wherein each of said independently movable elements has two or more spaced second profiles engaged by separate connecting elements engaging separate first profiles in the datum member to prevent any substantial angular rotation of the said independently movable elements.

76. A motion transmitting device as claimed in any of claims 46, 51 or 53 wherein each of said independently movable elements has two or more spaced second profiles engaged by separate connecting elements engaging separate first profiles in the datum member to prevent any substantial angular rotation of the said independently movable elements.

77. A motion transmitting device as claimed in any of claims 1, 38 or 39 wherein said first profiles are bearings permitting rotation of the connector elements in the datum member and said second profiles define the limits of orbital motion of the independently movable elements with respect to the datum member.

78. A motion transmitting device as claimed in any of claims 1, 38 or 39 wherein said second profiles are bearings permitting rotation of the connector elements in the independently movable elements and said first profiles define the limits of orbital motion of the independently movable or meshing elements with respect to the datum member.

79. A motion transmitting device as claimed in any of claims 46, 51 or 53 wherein either said first profiles are bearings permitting rotation of the connector elements in the datum member and said second profiles define the limits of orbital motion of the independently movable elements with respect to the datum member.

80. A motion transmitting device as claimed in any of claims 46, 51 or 53 wherein said second profiles are bearings permitting rotation of the connector elements in the independently movable elements and said first profiles define the limits of orbital motion of the independently movable or meshing elements with respect to the datum member.

81. A motion transmitting device as claimed in any of claims 1, 38 or 39 wherein of the three integers comprising the eccentric means, the wheel or gear means and the datum member, one is connected to a rotational input, another is connected to a rotational output and the third is fixed.

82. A motion transmitting device as claimed in any of claims 46, 51 or 53 wherein of the three integers comprising the eccentric means, the wheel or gear means and the datum member, one is connected to a rotational input, another is connected to a rotational output and the third is fixed.

83. A motion transmitting device as claimed in any of claims 1, 38 or 39 wherein the radius of said wheel means is the same as the radius of arc of an arcuate portion of an engaging face of each of said movable elements.

84. A motion transmitting device as claimed in any of claims 46, 51 or 53 wherein the radius of said wheel means is the same as the radius of arc of an arcuate portion of an engaging face of each of said movable elements.

85. A motion transmitting device as claimed in any of claims 11 or 38 or 39 wherein the number of teeth on said wheel means differs by unity from the number of teeth on said movable elements.

86. A motion transmitting device as claimed in any of claims 11 or 38 or 39 wherein the difference between the number of teeth on said wheel means and the number of teeth on said movable elements is greater than unity.

87. A motion transmitting device as claimed in any of claims 46 or 51 or 53 wherein the number of teeth on said wheel means differs by unity from the number of teeth on said movable elements.

38. A motion transmitting device as claimed in any of claims 46 or 51 or 53 wherein the difference between the number of teeth on said wheel means and the number of teeth on said movable elements is greater than unity.